The exact kind of test that reports the eGFR number this story is about.
National Eye InstituteCC BY 2.0
Illustrative, not from any of the three studies this story reports on.
Creatine Doesn't Hurt Your Kidneys. It Does Change Your Blood Test.
The single most persistent reason I hear from people who quit creatine, or never start it, is the kidneys. It is the first objection that comes up in almost every conversation about the supplement, and until recently the honest answer was messier than either side wanted it to be. Three separate research teams have now looked at this from three separate angles, and for the first time the evidence has actually converged on what is going on.
- Three independent systematic reviews and meta analyses, published in three separate journals across 2025 and 2026 from separate research teams, all reach the same conclusion about creatine and the kidneys.
- Creatine raises serum creatinine by an average of 0.14 mg per dL and lowers the eGFR number calculated from that creatinine, but when kidney filtration is measured directly instead of estimated, it does not decline.
- No meaningful differences turned up in urea, albumin, protein, or urinary creatinine, the other markers that would move if creatine were actually damaging the kidneys.
- The reassuring result was not statistically significant on its own, so the honest read is an absence of detected harm rather than definitive proof of safety, and evidence in pregnancy and lactation is still missing entirely.
The number that scares people is real. What it means is not what people think.
Creatine supplementation does raise serum creatinine, and it does lower the glomerular filtration rate number your doctor sees on a standard lab report, the one calculated from that same creatinine reading. A meta analysis published in July 2026 in the journal International Urology and Nephrology, pooling 26 randomized trials and 1,036 participants, found serum creatinine rose by an average of 0.14 mg per dL, with the creatinine based GFR estimate dropping by an average of 10.75 mL per minute. A second, fully independent review published in November 2025 in BMC Nephrology found the same direction of effect at a smaller size, and noted the change was concentrated in studies lasting a week or less, which points at the creatine loading phase as the period where the number moves the most.
Here is the part that actually resolves the argument. When the same researchers looked at glomerular filtration rate measured directly, using an injected marker called Cr EDTA rather than estimating it from a creatinine formula, the decline disappeared. There was no significant difference. Urea, albumin, protein, and urinary creatinine, the other markers that would be expected to move if the kidneys were actually under strain, did not change either.
Why the lab test cannot tell your creatine apart from kidney damage
The mechanism is almost boring once you see it. Creatine breaks down in the body into creatinine, and every formula doctors use to estimate kidney function, Cockcroft Gault, MDRD, CKD EPI, all of them, is built on measuring serum creatinine. Eat more creatine, produce more creatinine, and the formula reads that as reduced filtration, because creatinine is the only signal those equations know how to read. The authors of the July 2026 meta analysis put it plainly in their own conclusion: the changes seen "likely reflect altered creatinine metabolism rather than kidney injury, given the absence of changes when assessed using Cr EDTA." Your kidneys are not working harder or worse. The assay is just seeing the supplement.
Honest caveat
Be careful with how confident this gets stated, because the reassuring half of the evidence is also the weakest link. The directly measured GFR comparison, the one the whole "no kidney injury" conclusion rests on, landed at P equals .06, just outside the usual cutoff for statistical significance. That means the trials that measured filtration directly did not detect harm, which is a real and useful finding, but it is meaningfully weaker than proof that creatine has been shown not to affect the kidneys at all. There is also very high heterogeneity in the headline creatinine number itself, so 0.14 mg per dL should be read as a measurable rise across studies, not a number any one person should expect exactly. And the population limits are real: this evidence comes mostly from healthy adults and some patients with chronic kidney disease in short to medium term trials. Evidence in pregnancy and lactation is genuinely absent, and anyone with existing kidney disease should be making this decision with a clinician rather than a blog post.
What this means for you
If you take creatine and you have blood work coming up, the practical move is simple. Tell your doctor you supplement with creatine before they interpret your eGFR, particularly if you are in a loading phase or had blood drawn within a week or two of starting. You can also ask specifically about a cystatin C based eGFR, which does not depend on creatinine at all and will not be thrown off by the supplement the same way a standard panel is. None of this is a reason to start worrying about your kidneys if you already take creatine and feel fine. It is a reason to make sure the person reading your labs has the same information you do.
Primary sources
- Impact of creatine supplementation on kidney health: a systematic review and meta analysis. International Urology and Nephrology, July 27, 2026.
- Effect of creatine supplementation on kidney function: a systematic review and meta analysis. BMC Nephrology, November 6, 2025.
- The effect of creatine supplementation on kidney function: a systematic review and meta analysis of randomized controlled trials. Journal of Renal Nutrition, 2026.
Common questions
Does this mean creatine is proven safe for the kidneys?
Not quite, and the honest version matters. When kidney filtration was measured directly with Cr EDTA rather than estimated from creatinine, there was no significant decline, but that result landed at P equals .06, just short of the usual significance cutoff. That is an absence of detected harm in the trials that measured it directly, which is meaningfully weaker than a proof that creatine never affects the kidneys at all. Evidence is also genuinely lacking in pregnancy and lactation, and anyone with existing kidney disease should still make this decision with a clinician.
Why does creatine raise my creatinine number at all?
Creatine breaks down in your body into creatinine, and every eGFR formula doctors use, including Cockcroft Gault, MDRD, and CKD EPI, is built entirely on measuring serum creatinine. Take more creatine, make more creatinine, and the formula reads that as reduced kidney function because creatinine is the only signal it knows how to read. It is an accounting artifact of the assay, not evidence your kidneys are working harder or worse.
What should I actually tell my doctor?
Tell your doctor you take creatine before they interpret your eGFR, especially if you are in a loading phase or have had blood drawn within the past week of starting. You can also ask about a cystatin C based eGFR, which does not depend on creatinine at all and will not be thrown off by the supplement the same way.
Stay Curious.
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